Previously, there is known an offset fin manufacturing method that involves pressing of a plurality of punches against a strip plate, which is unwound and is fed from a roll of the strip plate, to form offset fins, each which has a cross section in a rectangular waveform and includes lateral surface portions that are alternately offset, JP2013-146736A (corresponding to US2013/0180698A1) discloses the offset fin manufacturing method of the above-described type. According to this method, a connection is formed in a strip plate at every predetermined interval in a feed direction of the strip plate, and a planar plate portion, which is located between corresponding two of the connections, is bent to produce an offset fin. Thereby, the offset fins, which are connected one after another by the connections, are continuously formed. Then, each corresponding one of the connections is cut at every predetermined number of the offset fins, to provide the predetermined number of the offset fins, which are connected one after another.
Lately, fin pitches of the offset fins have been progressively reduced to meet a demand of improving a heat exchange performance of the offset fins, and thereby a width of the connection, which connects between the offset fines, is also reduced. Because of this reason, at the time of transporting the offset fins, which are connected one after another by the connections, from, for example, a manufacturing factory to an assembling factory, there is a possibility of that the connections are broken and cut due to the insufficient strength of the connections. Thus, there is a difficulty of transporting the offset fins, which are connected one after another by the connections.